The herring harvest, through the careful and scientific methods that were employed in curing the fish and packing them in barrels, became a durable and much sought for article of commerce.

A small portion of the catch served as a supply of food for home consumption, the great bulk in its thousands of barrels was a marketable commodity, and the distribution of the cured herring to distant ports became a lucrative business.

It had two important consequences, the formation of a Dutch Mercantile Marine, and the growth of Amsterdam, which from small beginnings had in the middle of the sixteenth century become a town with 40,000 inhabitants and a port second only in importance in the Netherlands to Antwerp.

From its harbour at the confluence of the estuary of the Y with the Zuyder Zee ships owned and manned by Hollanders sailed along the coasts of France and Spain to bring home the salt for curing purposes and with it wines and other southern products, while year by year a still larger and increasing number entered the Baltic.

In those eastern waters they competed with the German Hanseatic cities, with whom they had many acrimonious disputes, and with such success that the Hollanders gradually monopolised the traffic in grain, hemp and other "Eastland" commodities and became practically the freight-carriers of the Baltic.
And be it remembered that they were able to achieve this because many of the North-Netherland towns were themselves members of the Hanse League, and possessed therefore the same rights and privileges commercially as their rivals, Hamburg, Luebeck or Danzig.